BACKGROUND:A recent Boo evolution, it's unclear where they originated. Balloon Boos, when spotted, begin sucking in air and swelling up at an alarming rate. After a certain amount of time they can't take any more air and simply sit there. Staring at you creepily. When you turn away they release the air out the other end and become normal sized again. Whilst not necessarilly dangerous in open spaces, the real trick is getting them to shrink so you can get past them before they reach critical mass again. Balloon Boos are invincible and can go through walls, like other Boos.